Dental Radiography Flashcards
Wall-mounted dental X-ray generator - adv
- Easier to use + position when learning dental radiography positioning as you are able to stand away to assess the position
- Easier to make adjustments, positioning isn’t quite correct as the X-ray head remains in the same position whilst the image is being generated
- Fewer concerns from RPAs (radiation protection advisors) usually as the operator is able to leave the room during an exposure
Handheld dental X-ray generator - adv
- If competent w/ positioning - quicker than wall-mounted
- Portable, can be moved around to diff rooms/places
Digital dental radiography - adv
- Inc magnification -> detailed clinical pathology
- Multiple exposures
- Reduced running costs
- Speed of image production
- Reduction in radiation doses
- Elimination of processing chemicals
Direct digital radiography (DR systems)
- Sensor connected directly to computer, usually via a wire
- Single size
- Very fast image production - 3 - 4 s on screen
- Sensor stays in position during image production and so positional changes are easier to assess
- Image quality: 25 – 33 lp/mm = resolution
Indirect digital radiography (CR)
- More similar to films - flexible + different sizes = adv, shapes + larger film than DR, useful in rabbits
- Film has to be removed from patient’s mouth for processing - 10 - 15 s
Image quality: - Dental specific: CR7 25 – 40 lp/mm
- CR converters: 5 – 8 lp/mm = low resolution
- Disadv - remove, film, would need to reposition, difficult for adjustments, slower process
Indications for dental x-rays
- Assess anatomy
- Periodontitis
- Pulp necrosis
- Dental Fx
- Tooth resorption
- Chronic gingivostomatitis/chronic ulcerative paradontal stomatitis
- Persistent deciduous teeth - roots resorbed - only crown of tooth that comes away
- Malocclusion
- Supernumerary/malerupted/unerupted teeth + dentigerous cysts
- Caries
Pathology
Dilaceration - abnormal bend in root/crown - change X process
Pathology
- Root anatomy
- Supernumerary third root in third pre-molar
Pathology
Supernumerary third root in cat’s fourth pre-molar
Pathology
Periodontal disease - horizontal + vertical bone loss
Pathology
- Periodontitis - external inflam root resorption, holes -> bacterial access to pulp inside tooth -> infected + necrotic -> peri-apical lucency around tooth root = black halo
- Periodontal disease
Pathology
- Pulp necrosis - wide pulp cavity, thin-walled dentin - tooth no longer producing dentin
- Open apex of pulp = immature tooth
- X or tooth root canal
Pathology
- Dental Fx
- Crown Fx -> pulp exposure
- Pulp exposure -> bacterial entry -> infection -> necrotic pulp -> stimulates peri-apical lucency associated w/ boen resorptioin
Pathology
Tooth resorption - common in cats
Pathology
- Chronic gingivostomatitis/chronic ulcerative paradontal stomatitis
- Cats - X all teeth, don’t want to leave anything behind
Pathology
- Persistent deciduous teeth - tooth root intact, X
- Usually spread through process of root absorption into bone, can be partly resorbed
Pathology
- Malocclusion
- E.g. Incisor teeth contacting palate + traumatising buccal mucosa -> X
Pathology
- Supernumerary/malerupted/unerupted teeth
- Make periosteal flap -> resect bone + X -> suture periosteal flap closed
Pathology
- Dentigerous cysts - result of unerupted tooth not being extracted
- Fluid builds up in jaw -> bone lysis -> loss of attachment of teeth -> v destructive lesions
Pathology
- Caries - tooth decay
- Less common - < 5% dogs, essentially non-existent in cats
- Erosion of tooth surface as result of bacterial fermentation of sugars - acid erodes into tooth -> exposure of pulp
- Pulp exposure -> infection -> necrosis -> inflam response around apex of tooth
Pathology
- Teeth associated w/ pathologic lesions
- E.g. Enamel dysplasia - browny tooth appearance (enamel = white)
- Bone loss
- Inflam response
Pathology
- Trauma - RTA
- E.g. Luxation of teeth in nasal cavity through alveolus
Importance of dental radiography in felines
- Dx of tooth resorption - to decide most appropriate Tx options
- Feline chronic gingivostomatitis (FCGS) - to determine whether extractions have been carried out successfully
Tooth resorption
- AKA - ‘neck lesions’, (feline) odontoclastic resorptive lesions (FORL)
- Abnormal destruction of dental hard tissues + its replacement w/ granulation tissue or bone
- High prevalence in cats - 25 - 40% -> 80% for any cats getting dental work done
Type 1 tooth resorption
- Associated w/ inflammation, present at cemento-enamel junction, tooth root unaffected
- Stimulates odontoclasts that eat into tooth surface cells -> loss of tooth structure
- Gingivitis, periodontal disease, gingival stomatitis
- Will need extracting from root
- See periodontal ligament
Type 2 tooth resorption
- Replacement resorption, cellular activity on root surface (odontoclasts inappropriately activated)
- Cells replaced w/ pink granulation tissue - changes tooth into bone
- Nothing to extract - just remove the crown / weakened at base, gum will just peel off, exposing bone/pulp, crown amputation speeds process up, gets teeth through painful part
- Fluffy appearance, cannot see periodontal ligament, nothing to extract
Type 3 tooth resorption
- Combination of type 1 & 2
- Inflam at cemento-enamel junction + replacement resorption - cellular activity on root surface
Cat - full mouth screening radiographs
Pathology
Pathology
Post-extraction - no root remnants (would be pot infection + pain)
Pathology
Pathology
Dental radipgraphy - Dx image criteria + techniques
- Accurate representation of size + shape of tooth w/o superimposition of adjacent structures
- Intra-oral radiographic techniques required
- Parallel technique = mandibular premolars + molars
- Bisecting angle technique - all other teeth
Parallel technique
- Film on table + patient parallel
- Beam perpendicular -> image develops on film
- Intra-oral sensor placed inside mouth between tongue + mandible -> sensor parallel to mandible
Bisecting angle technique
- For maxilla (bone of palate) + rostral part of mouth (mandibular symphysis)
- Beam directed 90 degrees to bisecting tooth angle (long axis of tooth from position of sensor)
Bisecting angle technique - incisors
Bisecting angle technique complications
- Elongation
- Shortening
Bisecting angle technique complications - elongation
- Creates artefacts
- If x-ray beam is directed at 90 degrees to the long axis of the tooth, the image is elongated
- Line of x-ray beam too shallow/obtuse
- Fix by raising beam up
Bisecting angle technique complications - shortening
- If x-ray beam is directed 90 degrees to the film, the image is foreshortened
- Too acute
- Fix by raising the beam down
Bisecting angle technique - mandibular canines (occlusal view)
Shows roof of mouth
Bisecting angle technique - maxillary canines (lateral view)
Bisecting angle technique - maxillary fourth premolar (carnassial - 108/208)
- Three-rooted tooth - approx idea of average angle of roots
- Use canine tooth for guide
Feline, bisecting angle technique - maxillary incisors
Feline, bisecting oblique angle - maxillary canine
Feline, bisecting angle - maxillary PMs + M
Feline, bisecting parallel angle - mandibular PMs + M
Feline - bisecting angle - mandibular canines + incisors
Feline, bisecting angle - mandibular canine teeth - lateral view
Canine - parallel, mandibular first molar
Canine - bisecting, mandibular canines (occlusal view)
Canine - bisecting, maxillary canines (lateral view)
Canine - bisecting, maxillary fourth PM
Feline - bisecting, maxillary incisors
Feline, bisecting, maxillary premolars + molar = cheek teeth view
Feline, bisecting, mandibular PMs + molar
Feline, bisecting, mandibular canines + incisors
Feline, bisecting, mandibular canine teeth, lateral view (+ 3 PMs)
Feline full-mouth screening
